A work machine including a dump truck operated in a mine is limited in traveling track thereof, and is forced to undergo passing and miss, and to approach other work machines including a hydraulic excavator. In particular, the work machine (mining machinery) utilized in the mine is large in size in many cases. Therefore, if the work machines bump each other when they approach each other, then, a big accident is caused in many cases, and thus a function of preventing a collision is strongly requested therefor. For collision prevention, it is necessary to know relative positions with respect to other machines, and thus a method of acquiring a relative position between a plurality of vehicles is disclosed in the prior art as well.
For example, in JP-2011-221869-A, there is disclosed a method with which a position (GPS position) where each vehicle measures individually by using a Global Positioning System (hereinafter referred to as a GPS) is communicated between two vehicles, thereby calculating a relative position between the two vehicles concerned. In addition, in JP-2007-164280-A, there is disclosed a method with which the GPS position measured by each machine is transmitted to a monitoring station, and is then distributed from the monitoring station to other machines. If these methods are used, then, the relative position between the vehicles can be calculated.